Input parameters needed to test for local light scattering closure
were initially discussed. Those inputs are: measured aerosol particle
(1) light scattering coefficient (2) refractive index, (3) mass
concentration, (4) mass density, and (5) wavelength of light scattered.
Such information is needed as a function of particle size. Once
refractive index and number concentration of the particles are
known as a function of actual size, then Mie light scattering
theory can be used to calculate the aerosols' light scattering
coefficients. Calculated and measured light scattering coefficients
can then be compared to evaluate closure.

Measured input parameters available by measurements made at Cape
Grim include:

All of the results listed above were submitted and made available
on Codiac by the completion of the workshop.

Future research will occur to analyze the impactor results to
determine the composition, hence refractive index, and then density
of the particles based on their particle size.

Future work:

Evaluate the differences between the mass and ion chromatographic
results of the impactor. Integrate data set to calculate light
scattering coefficients. Compare experimental and modeled results.

If the dry light scattering closure is encouraging, then it would
be useful evaluate light scattering closure as a function of relative
humidity. There were discussions to use measured particle size
growth curves, thermodynamic modeling, and metastable state modeling
to describe particle growth dependence on relative humidity.
These results could then be used with Mie Light scattering theory
to predict light scattering coefficient dependence on controlled
relative humidity. Closure could then be compared between modeled
and measured light scattering coefficient dependence on controlled
relative humidity.

Regional Characterization of Scattering Coefficients

Scattering coefficient results were compared between nephelometer
measurements at Cape Grim, Discover, and the C-130 aircraft.
Scattering coefficients [Mm-1] at 550 nm and particle diameters
< 1 µm were 0.6, 0.7, and 0.8, respectively, when the three
platforms were operating as close to each other as possible.
The arithmetic mean and standard deviation for the scattering
coefficients at 550 nm and particle diameter < 1 µm during all
measurements made at Cape Grim and Discoverer were 3.6± 1.9, and
4.1± 2.8, respectively. The arithmetic mean and standard deviation
for the scattering coefficients at 550 nm and particle diameter
< 10 µm during all measurements made at Cape Grim and Discoverer
were 15.4 ± 7.9, and 18 ± 12, respectively.

Future Work:

Data sets describing light scattering coefficients from Cape Grim,
Discover, and C-130 need to be carefully evaluated and integrated
to see how well the measurements were able to characterize the
region.